SILICONE COMPOSITION THAT CAN BE CROSS-LINKED TO FORM A SILICONE RESIN COMPOSITE MATERIAL

Abstract

Silicone resin having the general formula

##STR00001##

where R.sup.1 are identical or independently different monovalent hydrocarbon radicals or —OH and R.sup.2 are identical or independently different monovalent organofunctional hydrocarbon radicals, olefinically unsaturated hydrocarbon radicals or a hydrogen radical. Where R.sup.2 is bonded to the silicon atom via a carbon atom and R.sup.2 is a hydrogen radical that is bonded to the silicon atom directly. Where c is 0 or 1, (Ic) present in not less than 5 mol %, (Ia) present in not less than 20 mol %, (Ib) present in not more than 20 mol %, (Id) present in not more than 20 mol %. Not less than 1 mol % of units (Ic) contain a radical R.sup.2 that is a hydrogen radical and not less than 1 mol % of (Ic) contain radicals R.sup.2 that is an olefinically unsaturated hydrocarbon radical and includes pulverulent and fibrous fillers.

Claims

1-9. (canceled)

10. A silicone resin composition, comprising: wherein the silicone resin composition comprises a silicone resin (i) consisting of units of the general formula (Ia), (Ib), (Ic) and (Id) ##STR00003## wherein R.sup.1 are identical or independently different monovalent hydrocarbon radicals or —OH; wherein R.sup.2 are identical or independently different monovalent organofunctional hydrocarbon radicals, olefinically unsaturated hydrocarbon radicals or a hydrogen radical, where the radical R.sup.2 is bonded to the silicon atom via a carbon atom, and when R.sup.2 is a hydrogen radical, this is bonded to the silicon atom directly; wherein c has the value 0 or 1; wherein units (Ic) are present in a content of not less than 5 mol %; wherein units (Ia) are present in a content of not less than 20 mol %; wherein units (Ib) are present in a content of not more than 20 mol %; wherein units (Id) are present in a content of not more than 20 mol %; wherein not less than 1 mol % of units (Ic) contain a radical R.sup.2 that is a hydrogen radical; and wherein not less than 1 mol % of the units (Ic) contain a radical R.sup.2 that is an olefinically unsaturated hydrocarbon radical and also comprises both pulverulent fillers and fibrous fillers.

11. The silicone resin composition of claim 10, wherein in the silicone resin (i) the ratio of units of the general formula (Ic) in which the radical R.sup.2 is an olefinically unsaturated hydrocarbon radical to units in which the radical R.sup.2 is a hydrogen radical is 3:1 to 1:2.

12. The silicone resin composition of claim 10, wherein the pulverulent fillers have an average particle size from 0.1 μm to 0.3 mm.

13. The silicone resin composition of claim 10, wherein the pulverulent fillers are selected from fillers having a BET surface area of up to 50 m.sup.2/g and fillers having a BET surface area of not less than 50 m.sup.2/g.

14. The silicone resin composition of claim 10, wherein the fibrous fillers consist of particles in which the average ratio of length to diameter is not less than 5:1.

15. The silicone resin composition of claim 10, wherein the fibrous fillers are selected from natural fibres, man-made fibres and fibres from inorganic substances.

16. The silicone resin composition of claim 10, wherein the silicone resin comprises hydrosilylation catalyst selected from the metals platinum, rhodium, palladium, ruthenium and iridium and compounds thereof.

17. The silicone resin composition of claim 10, wherein the silicone resin comprises peroxide as crosslinker.

18. The silicone resin composition of claim 10, wherein a solid product is produced from the silicone resin composition.

Description

EXAMPLES

Example 1

[0122] The fillers are mixed homogeneously into 33.56 parts by weight of a self-crosslinking vinyl- and Si—H-functional methylphenyl resin composed of 46 mol % of TPh units (TPh=(C.sub.6H.sub.5)SiO.sub.3/2), 27 mol % of MH units (MH=H(CH.sub.3).sub.2SiO.sub.1/2) and 27 mol % of VM units (VM=(C.sub.2H.sub.3)(CH.sub.3).sub.2SiO.sub.1/2) that additionally contains 160 ppm by weight of OH units attached to the TPh units in a statistical distribution such that a Si-vinyl content of 2.64 mmol/g and a Si—H content of 2.61 mmol/g are obtained. Into this are mixed 0.84 parts by weight of 2,5-(tert-butylperoxy)-2,5-dimethylhexane and 0.42 parts by weight of a platinum catalyst and the mixture is first compressed at 135° C. After storage at 200° C. for a further 24 h, the material has been completely cured.

Example 2

[0123] The fillers are mixed homogeneously into 33.64 parts by weight of a self-crosslinking vinyl- and Si—H-functional methylphenyl resin composed of 46 mol % of TPh units (TPh=(C.sub.6H.sub.5)SiO.sub.3/2), 27 mol % of MH units (MH=H(CH.sub.3).sub.2SiO.sub.1/2) and 27 mol % of VM units (VM=(C.sub.2H.sub.3)(CH.sub.3).sub.2SiO.sub.1/2) that additionally contains 160 ppm by weight of OH units attached to the TPh units in a statistical distribution such that a Si-vinyl content of 2.64 mmol/g and a Si—H content of 2.61 mmol/g are obtained. Into this is mixed 1 part by weight of 2,5-(tert-butylperoxy)-2,5-dimethylhexane and the mixture is compressed at 165° C. After storage at 200° C. for a further 24 h, the material has been completely cured.

Example 3

[0124] The fillers are mixed homogeneously into 33.82 parts by weight of a self-crosslinking vinyl- and Si—H-functional methylphenyl resin composed of 46 mol % of TPh units (TPh=(C.sub.6H.sub.5)SiO.sub.3/2), 27 mol % of MH units (MH=H(CH.sub.3).sub.2SiO.sub.1/2) and 27 mol % of VM units (VM=(C.sub.2H.sub.3)(CH.sub.3).sub.2SiO.sub.1/2) that additionally contains 160 ppm by weight of OH units attached to the TPh units in a statistical distribution such that a Si-vinyl content of 2.64 mmol/g and a Si—H content of 2.61 mmol/g are obtained. Into this is mixed 0.5 parts by weight of a platinum catalyst and the mixture is compressed at 135° C. After storage at 200° C. for a further 24 h, the material has been completely cured.

Example 4 (Noninventive)

[0125] The procedure described in Example 2 is followed, but without the addition of fillers. After crosslinking for 15 minutes at 165° C., crosslinked resin without reinforcing fillers shows low mechanical strength, which can be improved slightly through heat-treatment. The flexural strength of the crosslinked resin before heating is only 1 MPa, the tensile strength is less than 1 N/mm.sup.−2. Heat-treatment increases the mechanical strength. After heat-treating at 200° C. for 24 h, flexural strength of 8 MPa and tensile strength of 6 N/mm.sup.−2 are achieved. The resin nonetheless cannot be used for producing moulded parts, because it is brittle.

Example 5 (Noninventive)

[0126] The procedure described in Example 2 is followed. The mixture of binder with quartz customary in casting resins results, as expected, in an improvement in mechanical properties. For example, a mixture of 40 parts of the described silicone resin with 65 parts of quartz of the Sikron SF 4000 type (cristobalite, average particle size 5 μm) achieves, after heat-treating at 200° C. for 24 h, a flexural strength of 25 MPa and a tensile strength of 19 N/mm.sup.−2.

Example 6 (Noninventive)

[0127] The procedure described in Example 2 is followed. The experimental incorporation of up to 65 parts of milled short glass fibres (Lanxess MF 7986 with diameter 16 μm, average fibre length 220 μm, type E glass (DIN 1259)) into the silicone resin binder results always in the formation of a sometimes felt-like, highly viscous, inhomogeneous, unprocessable mixture. On standing for a short period and particularly after shaking, the binder separates from the fibres.

[0128] The result of the experimental crosslinking demonstrates that it is not possible to produce moulded parts having a homogeneous fibre-binder distribution.

Example 7 (Inventive)

[0129] The procedure described in Example 2 is followed. A mixture of 25 parts of short glass fibres, 25 parts of quartz and 15 parts of colloidal silica (Wacker HDK H 2000) is incorporated into the silicone resin as binder and the mixture is crosslinked and heat-treated at 200° C. for 24 h. A flexural strength of >50 MPa and tensile strength of >25 N/mm.sup.−2 are achieved.

[0130] The additional addition of quartz powder to the glass fibre-binder mixture in accordance with Example 6 surprisingly affords a mixture that is no longer felt-like and in which the binder no longer has a tendency to separate, and which has lower viscosity than before addition of the quartz powder, is easily processed and can be used to produce homogeneous shaped bodies. The mechanical properties were improved further compared with use of quartz on its own. In the silicone resin-binder mixture, contrary to expectations it was found that glass fibres and quartz, and even the addition of colloidal silica, results in a further improvement in appearance (no separation), in processability and in mechanical properties.